1. Field of the Invention
The present invention relates to a composition of a positive photosensitive polyimide precursor, which is suitable as a surface protective layer and interlayer dielectric of a semiconductor device and an insulating layer of an organic electroluminescent device. In the resulting positive photosensitive polyimide precursor, exposed portions irradiated with ultraviolet rays are dissolved in an alkaline aqueous solution.
2. Description of the Related Art
Known compositions of positive heat-resistant resin precursors, in which exposed portions are dissolved by alkali-development, include a composition containing a polyamic acid with a naphthoquinonediazide, a composition containing a soluble polyimide having a hydroxyl group with a naphthoquinonediazide, and a composition containing a polyamide having a hydroxyl group with a naphthoquinonediazide.
However, such a composition containing a conventional polyamic acid with a naphthoquinonediazide cannot yield a desired pattern in most cases, since high solubility of the carboxyl group of the polyamic acid overcomes dissolution-inhibitory effect of the naphthoquinonediazide to an alkaline developer. In order to control the alkaline solubility of a polyamic acid, a polyamic acid derivative in which the carboxyl group of the polyamic acid is protected with an ester group has been developed.
However, a composition containing the above polyamic acid derivative with a naphthoquinonediazide exhibits very high dissolution-inhibitory effect to an alkaline developer due to the naphthoquinonediazide, therefore cannot be developed in a short time (hereinafter referred to as xe2x80x9clow sensitivityxe2x80x9d) and cannot yield a fine pattern with a high resolution (hereinafter referred to as xe2x80x9clow resolutionxe2x80x9d) in most cases, whereas it can yield a desired pattern.
Specifically, the present invention provides, in an aspect, a composition of a positive photosensitive resin precursor (hereinafter briefly referred to as xe2x80x9cresin compositionxe2x80x9d or xe2x80x9cprecursor compositionxe2x80x9d), including (a) a polyamic acid ester and/or a polyamic acid each having at least one of a carboxyl group, a phenolic hydroxyl group, a sulfonic acid group, a thiol group and combinations thereof at the end of a principal chain of the polymer, (b) a compound having a phenolic hydroxyl group and (c) a quinonediazide sulfonate.
In another aspect, the present invention provides a display device including a substrate, a first electrode formed on the substrate, an insulating layer formed on the first electrode in such a manner that part of the first electrode is exposed, and a second electrode facing the first electrode, in which the insulating layer includes the aforementioned resin composition.
The resin composition of the present invention can be developed in an alkaline aqueous solution, exhibits excellent resolution, sensitivity and film residual rate and can specifically advantageously used as an insulating layer of a display.
The present inventors have found that a resin composition containing a compound having a phenolic hydroxyl group and a naphthoquinonediazide compound in addition to a polyimide precursor is dissolved little in an alkali developer before exposure and is readily dissolved in the alkali developer after exposure, which polyimide precursor is synthetically obtained by using an endcapping agent having an alkali-soluble group. This resin composition exhibits less reduction in film thickness due to development, can be developed in a short time (hereinafter referred to as xe2x80x9chigh sensitivityxe2x80x9d) and can yield a fine pattern (hereinafter referred to as xe2x80x9chigh resolutionxe2x80x9d). The present invention has been accomplished based on these findings.
Polyamic acid esters for use in the present invention can become polymers each having an imide ring structure by heat or by catalysis of an appropriate catalyst. The resulting polymers each have an imide ring structure and have significantly improved heat resistance and solvent resistance. 
In Formulae (1), (2), (3) and (4), R1 is an organic group having a valency of 4; R2 is an organic group having a valency of from 2 to 4; R3 is a hydrogen atom and/or an organic group having from 1 to 20 carbon atoms; R4 is an organic group having a valency of 2; X is an organic group having at least one of a carboxyl group, a phenolic hydroxyl group, a sulfonic acid group and a thiol group and having a valency of from 2 to 8; n is an integer from 10 to 100000; and m is an integer from 0 to 10.
The component R1 in Formulae (1), (2), (3) and (4) represents a structural component of a dianhydride. The dianhydride is preferably a tetravalent organic group having an aromatic ring or an aliphatic ring and having a valency of from 4, of which an organic group having from 5 to 40 carbon atoms is typically preferred.
Such dianhydrides include, but are not limited to, pyromellitic dianhydride, 3,3xe2x80x2,4,4xe2x80x2-biphenyltetracarboxylic dianhydride, 2,3,3xe2x80x2,4xe2x80x2-biphenyltetracarboxylic dianhydride, 2,2xe2x80x2,3,3xe2x80x2-biphenyltetracarboxylic dianhydride, 3,3xe2x80x2,4,4xe2x80x2-benzophenonetetracarboxylic dianhydride, 2,2xe2x80x2,3,3xe2x80x2-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl) sulfone dianhydride, bis(3,4-dicarboxyphenyl) ether dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, and other aromatic tetracarboxylic dianhydrides; and butanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, and other aliphatic tetracarboxylic dianhydrides. Among them, 3,3xe2x80x2,4,4xe2x80x2-biphenyltetracarboxylic dianhydride, 2,3,3xe2x80x2,4xe2x80x2-biphenyltetracarboxylic dianhydride, 2,2xe2x80x2,3,3xe2x80x2-biphenyltetracarboxylic dianhydride, 3,3xe2x80x2,4,4xe2x80x2-benzophenonetetracarboxylic dianhydride, 2,2xe2x80x2,3,3xe2x80x2-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl) sulfone dianhydride, bis(3,4-dicarboxyphenyl) ether dianhydride, and 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride are preferred. Each of these components can be used alone or in combination.
The component R2 in Formulae (1), (2), (3) and (4) represents a structural component of a diamine. Such diamines are preferably organic groups each having an aromatic ring or an aliphatic ring and having a valency of from 2 to 4, of which organic groups each having from 5 to 40 carbon atoms are typically preferred.
Such diamines include, but are not limited to, 3,4xe2x80x2-diaminodiphenyl ether, 4,4xe2x80x2-diaminodiphenyl ether, 3,4xe2x80x2-diaminodiphenylmethane, 4,4xe2x80x2-diaminodiphenylmethane, 3,4xe2x80x2-diaminodiphenyl sulfone, 4,4xe2x80x2-diaminodiphenyl sulfone, 3,4xe2x80x2-diaminodiphenyl sulfide, 4,4xe2x80x2-diaminodiphenyl sulfide, 1,4-bis(4-aminophenoxy)benzene, benzidine, m-phenylenediamine, p-phenylenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, bis(4-aminophenoxyphenyl) sulfone, bis(3-aminophenoxyphenyl) sulfone, bis(4-aminophenoxy)biphenyl, bis{4-(4-aminophenoxy)phenyl}ether, 2,2xe2x80x2-dimethyl-4,4xe2x80x2-diaminobiphenyl, 2,2xe2x80x2-diethyl-4,4xe2x80x2-diaminobiphenyl, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-diaminobiphenyl, 3,3xe2x80x2-diethyl-4,4xe2x80x2-diaminobiphenyl, 2,2xe2x80x2,3,3xe2x80x2-tetramethyl-4,4xe2x80x2-diaminobiphenyl, 3,3xe2x80x2,4,4xe2x80x2-tetramethyl-4,4xe2x80x2-diaminobiphenyl, 2,2xe2x80x2-di(trifluoromethyl)-4,4xe2x80x2-diaminobiphenyl, compounds in which an alkyl group or a halogen atom is substituted on these aromatic rings, and other aromatic diamines; and cyclohexyldiamines, methylenebiscyclohexylamine, and other aliphatic diamines.
Among them, 3,4xe2x80x2-diaminodiphenyl ether, 4,4xe2x80x2-diaminodiphenyl ether, 3,4xe2x80x2-diaminodiphenylmethane, 4,4xe2x80x2-diaminodiphenylmethane, 3,4-diaminodiphenyl sulfone, 4,4xe2x80x2-diaminodiphenyl sulfone, 3,4xe2x80x2-diaminodiphenyl sulfide, 4,4xe2x80x2-diaminodiphenyl sulfide, m-phenylenediamine, p-phenylenediamine and 1,4-bis (4-aminophenoxy)benzene are preferred, of which 3,4xe2x80x2-diaminodiphenyl ether, 4,4xe2x80x2-diaminodiphenyl ether, 3,4xe2x80x2-diaminodiphenylmethane, 4,4xe2x80x2-diaminodiphenylmethane, 3,4xe2x80x2-diaminodiphenyl sulfone, 4,4xe2x80x2-diaminodiphenyl sulfone and 1,4-bis(4-aminophenoxy)benzene are typically preferred. Each of these components is used alone or in combination.
The substituent R3 in Formulae (1), (2), (3) and (4) represents a hydrogen atom and/or an organic group having from 1 to 20 carbon atoms. As R3, organic groups are preferred from the view point of the stability of the resulting positive photosensitive resin precursor solution, but hydrogen atoms are preferred from the view point of the solubility of the resulting resin precursor in an aqueous alkaline solution. The substituents R3 S may be a hydrogen atom and an organic group in combination in the present invention. By controlling the ratio of the hydrogen atom to the organic group in R3, the dissolution rate of the resulting resin precursor in an alkaline aqueous solution changes and thereby yields a composition of a positive photosensitive resin precursor having an appropriate dissolution rate. The hydrogen atom preferably occupies from 10% to 90% of the substituents R3s. If the organic group as R3 has more than 20 carbon atoms, the resulting resin becomes in soluble in an alkaline aqueous solution. Accordingly, R3s more preferably comprise at least one hydrocarbon group having from 1 to 16 carbon atoms with the balance of hydrogen atoms.
The structural component xe2x80x94NHxe2x80x94(R4)mxe2x80x94X in Formulae (1) and (2) is preferably one represented by following Formula (8), and this component is derived from a primary monoamine serving as an endcapping agent. The substituent X is preferably an organic group having at least one of a carboxyl group, a phenolic hydroxyl group, a sulfonic acid group and a thiol group and having a valency of from 2 to 8 and is more preferably an organic group having at least one of a carboxyl group, a phenolic hydroxyl group and a thiol group and having a valency of from 2 to 8. 
The structural component xe2x80x94COxe2x80x94(R4)mxe2x80x94Y in Formulae (3) and (4) is preferably one of components represented by Formula (9) and (10), and these components are derived from one of anhydrides, monocarboxylic acids, mono(acid chloride) compounds and mono-active esters each serving as an endcapping agent. The substituent Y is preferably an organic group having at least one of a carboxyl group, a phenolic hydroxyl group, a sulfonic acid group and a thiol group and having a valency of from 2 to 8 and is more preferably an organic group having at least one of a carboxyl group, a phenolic hydroxyl group and a thiol group and having a valency of from 2 to 8. The components Ys in Formulae (3) and (4) comprise the endcapping group represented by Formula (9) alone, the endcapping group represented by Formula (10) alone, or both the endcapping groups represented by Formulae (9) and (10) in combination. 
In Formulae (8), (9) and (10), R4 is a divalent group selected from xe2x80x94CR18R19xe2x80x94, xe2x80x94CH2Oxe2x80x94 and xe2x80x94CH2SO2xe2x80x94; and R18 and R19 are each a monovalent group selected from a hydrogen atom, a hydroxyl group and hydrocarbon groups each having from 1 to 10 carbon atoms. The R15 is a monovalent group selected from a hydrogen atom and a hydrocarbon group having from 1 to 10 carbon atoms and is preferably selected from a hydrogen atom and a hydrocarbon group having from 1 to 4 carbon atoms, of which a hydrogen atom, methyl group and t-butyl group are typically preferred. The substituents R16 and R17 are each a monovalent group selected from a hydrogen atom and hydrocarbon groups each having from 1 to 4 carbon atoms, or are directly combined with each other to form a ring structure such as a nadimide ring. The substituents R13 and R14 are each selected from a hydrogen atom, a hydroxyl group, a carboxyl group, a sulfonic acid group, a thiol group and a hydrocarbon group having from 1 to 10 carbon atoms, where at least one of R13 and R14 is a hydroxyl group, a carboxyl group, a sulfonic acid group or a thiol group. A1, B1 and C1 are the same or different and are each a carbon atom or a nitrogen atom. The repetition number m is an integer from 0 to 10 and is preferably an integer from 0 to 4. The number 1 is 0 or 1 and is preferably 0. The number p is 0 or 1 and is preferably 0. The repetition number q is an integer from 1 to 3 and is preferably 1 or 2. The numbers r, s and t are each 0 or 1.
Examples of primary monoamines corresponding to Formula (8) include 5-amino-8-hydroxyquinoline, 4-amino-8-hydroxyquinoline, 1-hydroxy-8-aminonaphthalene, 1-hydroxy-7-aminonaphthalene, 1-hydroxy-6-aminonaphthalene, 1-hydroxy-5-aminonaphthalene, 1-hydroxy-4-aminonaphthalene, 1-hydroxy-3-aminonaphthalene, 1-hydroxy-2-aminonaphthalene, 1-amino-7-hydroxynaphthalene, 2-hydroxy-7-aminonaphthalene, 2-hydroxy-6-aminonaphthalene, 2-hydroxy-5-aminonaphthalene, 2-hydroxy-4-aminonaphthalene, 2-hydroxy-3-aminonaphthalene, 1-amino-2-hydroxynaphthalene, 1-carboxy-8-aminonaphthalene, 1-carboxy-7-aminonaphthalene, 1-carboxy-6-aminonaphthalene, 1-carboxy-5-aminonaphthalene, 1-carboxy-4-aminonaphthalene, 1-carboxy-3-aminonaphthalene, 1-carboxy-2-aminonaphthalene, 1-amino-7-carboxynaphthalene, 2-carboxy-7-aminonaphthalene, 2-carboxy-6-aminonaphthalene, 2-carboxy-5-aminonaphthalene, 2-carboxy-4-aminonaphthalene, 2-carboxy-3-aminonaphthalene, 1-amino-2-carboxynaphthalene, 2-aminonicotinic acid, 4-aminonicotinic acid, 5-aminonicotinic acid, 6-aminonicotinic acid, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 3-amino-o-toluic acid, ammelide, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, 2-aminobenzenesulfonic acid, 3-aminobenzenesulfonic acid, 4-aminobenzenesulfonic acid, 3-amino-4,6-dihydroxypyrimidine, 2-aminophenol, 3-aminophenol, 4-aminophenol, 5-amino-8-mercaptoquinoline, 4-amino-8-mercaptoquinoline, 1-mercapto-8-aminonaphthalene, 1-mercapto-7-aminonaphthalene, 1-mercapto-6-aminonaphthalene, 1-mercapto-5-aminonaphthalene, 1-mercapto-4-aminonaphthalene, 1-mercapto-3-aminonaphthalene, 1-mercapto-2-aminonaphthalene, 1-amino-7-mercaptonaphthalene, 2-mercapto-7-aminonaphthalene, 2-mercapto-6-aminonaphthalene, 2-mercapto-5-aminonaphthalene, 2-mercapto-4-aminonaphthalene, 2-mercapto-3-aminonaphthalene, 1-amino-2-mercaptonaphthalene, 3-amino-4,6-dimercaptopyrimidine, 2-aminothiophenol, 3-aminothiophenol, and 4-aminothiophenol.
Among them, preferred are 5-amino-8-hydroxyquinoline, 1-hydroxy-7-aminonaphthalene, 1-hydroxy-6-aminonaphthalene, 1-hydroxy-5-aminonaphthalene, 1-hydroxy-4-aminonaphthalene, 2-hydroxy-7-aminonaphthalene, 2-hydroxy-6-aminonaphthalene, 2-hydroxy-5-aminonaphthalene, 1-carboxy-7-aminonaphthalene, 1-carboxy-6-aminonaphthalene, 1-carboxy-5-aminonaphthalene, 2-carboxy-7-aminonaphthalene, 2-carboxy-6-aminonaphthalene, 2-carboxy-5-aminonaphthalene, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 2-aminobenzenesulfonic acid, 3-aminobenzenesulfonic acid, 4-aminobenzenesulfonic acid, 3-amino-4,6-dihydroxypyrimidine, 2-aminophenol, 3-aminophenol, 4-aminophenol, 2-aminothiophenol, 3-aminothiophenol and 4-aminothiophenol. Each of these components can be used alone or in combination.
Acid anhydrides, monocarboxylic acids, mono(acid chloride) compounds and mono-active esters corresponding to Formulae (9) and (10) include, but are not limited to, phthalic anhydride, maleic anhydride, nadic acid, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, and other acid anhydrides; 2-carboxyphenol, 3-carboxyphenol, 4-carboxyphenol, 2-carboxythiophenol, 3-carboxythiophenol, 4-carboxythiophenol, 1-hydroxy-8-carboxynaphthalene, 1-hydroxy-7-carboxynaphthalene, 1-hydroxy-6-carboxynaphthalene, 1-hydroxy-5-carboxynaphthalene, 1-hydroxy-4-carboxynaphthalene, 1-hydroxy-3-carboxynaphthalene, 1-hydroxy-2-carboxynaphthalene, 1-mercapto-8-carboxynaphthalene, 1-mercapto-7-carboxynaphthalene, 1-mercapto-6-carboxynaphthalene, 1-mercapto-5-carboxynaphthalene, 1-mercapto-4-carboxynaphthalene, 1-mercapto-3-carboxynaphthalene, 1-mercapto-2-carboxynaphthalene, 2-carboxybenzenesulfonic acid, 3-carboxybenzenesulfonic acid, 4-carboxybenzenesulfonic acid, and other monocarboxylic acids, and mono(acid chloride)s in which carboxyl groups of these monocarboxylic acids are converted into acid chlorides; mono(acid chloride) compounds, in which one carboxyl group alone of a dicarboxylic acid is converted into an acid chloride, derived from dicarboxylic acids such as terephthalic acid, phthalic acid, maleic acid, cyclohexanedicarboxylic acid, 3-hydroxyphthalic acid, 5-norbornene-2,3-dicarboxylic acid, 1,2-dicarboxynaphthalene, 1,3-dicarboxynaphthalene, 1,4-dicarboxynaphthalene, 1,5-dicarboxynaphthalene, 1,6-dicarboxynaphthalene, 1,7-dicarboxynaphthalene, 1,8-dicarboxynaphthalene, 2,3-dicarboxynaphthalene, 2,6-dicarboxynaphthalene, 2,7-dicarboxynaphthalene, and other dicarboxylic acids; and active esters obtained by the reaction between a mono(acid chloride) compound and N-hydroxybenzotriazole or N-hydroxy-5-norbornene-2,3-dicarboximide.
Among them, preferred are phthalic anhydride, maleic anhydride, nadic acid, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, and other acid anhydrides; 3-carboxyphenol, 4-carboxyphenol, 3-carboxythiophenol, 4-carboxythiophenol, 1-hydroxy-7-carboxynaphthalene, 1-hydroxy-6-carboxynaphthalene, 1-hydroxy-5-carboxynaphthalene, 1-mercapto-7-carboxynaphthalene, 1-mercapto-6-carboxynaphthalene, 1-mercapto-5-carboxynaphthalene, 3-carboxybenzenesulfonic acid, 4-carboxybenzenesulfonic acid, and other monocarboxylic acids, and mono(acid chloride)s in which carboxyl groups of these monocarboxylic acids are converted into acid chlorides; mono(acid chloride) compounds in which one carboxyl group alone of a dicarboxylic acid is converted into an acid chloride, derived from dicarboxylic acids such as terephthalic acid, phthalic acid, maleic acid, cyclohexanedicarboxylic acid, 1,5-dicarboxynaphthalene, 1,6-dicarboxynaphthalene, 1,7-dicarboxynaphthalene, 2,6-dicarboxynaphthalene, and other dicarboxylic acids; and active esters obtained by the reaction between a mono(acid chloride) and N-hydroxybenzotriazole or N-hydroxy-5-norbornene-2,3-dicarboximide. Each of these components can be used alone or in combination.
The proportion of the component represented by Formula (8), i.e., xe2x80x94NHxe2x80x94(R4)mxe2x80x94X as the structural component in Formulae (1) and (2), is preferably from 0.1% to 60% by mole and more preferably from 5% to 50% by mole in terms of the primary monoamine component of the endcapping agent as the source component, relative to the total amine components.
The proportion of the component represented by Formula (9) or (10), i.e., xe2x80x94COxe2x80x94(R4)mxe2x80x94Y as the structural component in Formulae (3) and (4), is preferably from 0.1% to 60% by mole and more preferably from 5% to 55% by mole in terms of the acid anhydride, monocarboxylic acid, mono(acid chloride) compound or mono-active ester compound component of the endcapping agent as the source component, relative to the total diamine components.
In Formulae (1), (2), (3) and (4), n is a repeating number of the structural repeating unit of the polymer component (a) according to the present invention and is preferably from 10 to 100000.
To improve adhesion to substrates, an aliphatic group having a siloxane structure can be copolymerized with R1 and/or R2 within a range not deteriorating heat resistance. Examples of such polymers include copolymers each comprising 1% to 10% by mole of bis(3-aminopropyl)tetramethyldisiloxane or bis(p-amino-phenyl)octamethylpentasiloxane as the diamine component.
The component (a) of the resin composition of the present invention may comprise the structural units represented by Formula (1) and/or (2) or those represented by Formula (3) and/or (4) alone or may be copolymers or blends with other structural units. In this case, the resulting polymer include equal to or more than 50% by mole of the structural unit(s) represented by Formula (1) and/or (2) or those represented by Formula (3) and/or (4). The types and amounts of structural units for use in copolymerization or blending are preferably selected within ranges not deteriorating heat resistance of the resulting polyimide polymer ultimately obtained by heat treatment.
The heat-resistant resin precursor (a) according to the present invention is synthetically obtained in a conventional manner by replacing part of a diamine with a monoamine serving as an endcapping agent or by replacing a dianhydride with a monocarboxylic acid, acid anhydride, mono(acid chloride) or mono-active ester compound serving as the endcapping agent. For example, the heat-resistant resin precursor (a) can be obtained by a process in which a tetracarboxylic dianhydride is allowed to react with a diamine compound (part of which is substituted with a monoamine serving as the endcapping agent) at low temperatures; a process in which a tetracarboxylic dianhydride (part of which is replaced with a mono(acid chloride) compound or mono-active ester compound serving as the endcapping agent) is allowed to react with a diamine compound at low temperatures; a process in which a tetracarboxylic dianhydride is allowed to react with an alcohol to yield a diester, and the diester is allowed to react with a diamine (part of which is replaced with a monoamine serving as the endcapping agent) in the presence of a condensing agent; or a process in which a tetracarboxylic dianhydride is allowed to react with an alcohol to yield a diester, the remainder dicarboxylic acid is converted into an acid chloride, and the acid chloride is allowed to react with a diamine (part of which is replaced with a monoamine serving as the endcapping agent).
The endcapping agent introduced into the polymer (a) for use in the present invention can easily be detected by the following techniques. For example, the endcapping agent can easily be detected by dissolving the polymer having the introduced endcapping agent in an acidic solution and thereby decomposing the same into an amine component and an anhydride component as structural units of the polymer, and analyzing these components by means of gas chromatography (GC) or nuclear magnetic resonance (NMR). Alternatively, the endcapping agent can easily be detected by directly subjecting the polymer component having the introduced endcapping agent to pyrolysis gas chromatography (PGC) or determination of an infrared spectrum and 13C-NMR spectrum.
Compounds each having a phenolic hydroxyl group for use in the present invention include, but are not limited to, those available as Bis-Z, BisOC-Z, BisOPP-Z, BisP-CP, Bis26X-Z, BisOTBP-Z, BisOCHP-Z, BisOCR-CP, BisP-MZ, BisP-EZ, Bis26X-CP, BisP-PZ, BisP-IPZ, BisCR-IPZ, BisOCP-IPZ, BisOIPP-CP, Bis26X-IPZ, BisOTBP-CP, TekP-4HBPA (TetrakisP-DO-BPA), TrisP-HAP, TrisP-PA, BisOFP-Z, BisRS-2P, BisPG-26X, BisRS-3P, BisOC-OCHP, BisPC-OCHP, Bis25X-OCHP, Bis26X-OCHP, BisOCHP-OC, Bis236T-OCHP, Methylenetris-FR-CR, BisRS-26X and BisRS-OCHP (trade names, available from Honshu Chemical Industry Co., Ltd.), BIR-OC, BIP-BIOC-F and TEP-BIP-A (trade names, available from Asahi Organic Chemicals Industry Co., Ltd.).
The compounds each having a phenolic hydroxyl group are preferably compounds represented by following Formula (5): 
wherein R5 to R8 are each a hydrogen atom, a hydroxyl group, an alkyl group having from 1 to 20 carbon atoms or an alicyclic group having from 4 to 20 carbon atoms; and a is an integer from 0 to 5. Preferably, R7 and R8 are preferably each an alicyclic group having from 4 to 20 carbon atoms.
Such compounds represented by Formula (5) are available, for example, as BisPC-PCHP, BisRS-PEP, BisTBC-PC, Bis24X-PC, Bis35X-PC, Methylenebis-p-CR, o,oxe2x80x2-BPF, oo-BisOC-F, oo-Bis25X-F, MB-PIPP, BisMHQ-F and Bis24X-F (trade names, available from Honshu Chemical Industry Co., Ltd.), BIHQ-PC, BI2MR-PC, BI4MC-PC, BIR-34X, BIR-PAP, BIPC-PC, BIR-PC, BIR-PTBP, BIR-PCHP, 4PC and BIR-BIPC-F (trade names, available from Asahi Organic Chemicals Industry Co., Ltd.).
Alternatively, the compounds each having a phenolic hydroxyl group are preferably thermally cross-linkable compounds each having an organic group represented by Formula (6):
xe2x80x94CH2xe2x80x94OR9xe2x80x83xe2x80x83(6) 
wherein R9 is a hydrogen atom, an alkyl group having from 1 to 20 carbon atoms, an alicyclic group having from 4 to 20 carbon atoms, or an R10CO group, where R10 is an alkyl group having from 1 to 20 carbon atoms. The substituent R9 is preferably an alkyl group having from 1 to 20 carbon atoms or an alicyclic group having from 4 to 20 carbon atoms.
Such thermally cross-linkable compounds each having one group represented by Formula (6) are available as ML-26X, ML-24X, ML-236TMP, 4-Methylol3M6C, ML-TC and ML-TBC (trade names, available from Honshu Chemical Industry Co., Ltd.). Those each having two groups represented by Formula (6) are available as DM-BI25X-F (trade name, available from Asahi Organic Chemicals Industry Co., Ltd.), DML-MBPC, DML-MBOC, Dimethylol-Bis-C, Dimethylol-BisOC-P, DML-BisOC-Z, DML-BisOCHP-Z, DML-MB25, DML-MTrisPC, DML-Bis25X-34XL and DML-Bis25X-PCHP (trade names, available from Honshu Chemical Industry Co., Ltd.); those each having three organic groups represented by Formula (6) are available as, for example, TriML-P, TriML-35XL and TriML-TrisCR-HAP (trade names, available from Honshu Chemical Industry Co., Ltd.); those having four organic groups represented by Formula (6) are available as, for example, TM-BIP-A (trade name, available from Asahi Organic Chemicals Industry Co., Ltd.), TML-BP, TML-HQ, TML-pp-BPF, TML-BPA and TMOM-BP (trade names, available from Honshu Chemical Industry Co., Ltd.); those each having six organic groups represented by Formula (6) are available as, for example, HML-TPPHBA and HML-TPHAP (trade names, available from Honshu Chemical Industry Co., Ltd.).
The thermally cross-linkable compounds each having the organic group represented by Formula (6) are preferably compounds represented by following Formula (7): 
wherein R9 has the same meaning as defined above; and R11 and R12 are each a hydrogen atom, an alkyl group having from 1 to 20 carbon atoms, an alicyclic group having from 4 to 20 carbon atoms or an R13xe2x80x2COO group, where R13xe2x80x2 is an alkyl group having from 1 to 20 carbon atoms.
Such compounds represented by Formula (7) each having two organic groups represented by Formula (6) include, for example, 46DMOC, 46DMOIPP, 46DMOEP and 46DMOCHP (trade names, available from Asahi Organic Chemicals Industry Co., Ltd.), DML-OCHP, DML-PC, DML-PCHP, DML-PTBP, DML-34X, DML-EP, DML-POP, DML-OC, DML-PFP and DML-PSBP (trade names, available from Honshu Chemical Industry Co., Ltd.), 2,6-dimethoxymethyl-4-t-butylphenol, 2,6-dimethoxymethyl-p-cresol and 2,6-diacetoxymethyl-p-cresol.
Of these compounds each having a phenolic hydroxyl group, preferred compounds are Bis-Z, BisP-EZ, TekP-4HBPA, TrisP-HAP, TrisP-PA, BisOCHP-Z, BisP-MZ, BisP-PZ, BisP-IPZ, BisOCP-IPZ, BisP-CP, BisRS-2P, BisRS-3P, BisP-OCHP, Methylenetris-FR-CR, and BisRS-26X; the compounds represented by Formula (5) such as BisPC-PCHP, BisTBC-PC, Bis35X-PC, Methylenebis-p-CR, o,oxe2x80x2-BPF, MB-PIPP, BisMHQ-F and Bis24X-F (trade names, available from Honshu Chemical Industry Co., Ltd.), BI2MR-PC, BI4MC-PC, BIR-PAP, BIPC-PC, BIR-PC, BIR-PTBP, BIR-PCHP, 4PC and BIR-BIPC-F (trade names, available from Asahi Organic Chemicals Industry Co., Ltd.); the thermally cross-linkable compounds each having two organic groups represented by Formula (6) such as DML-MBPC, DML-MBOC, Dimethylol-BisOC-P, DML-MTrisPC, and the compounds represented by Formula (7) such as 46DMOC, 46DMOEP, 46DMOCHP, DML-OCHP, DML-PC, DML-PCHP, DML-PTBP, DML-34X, DML-EP, DML-POP, DML-PFP, DML-PSBP, 2,6-dimethoxymethyl-4-t-butylphenol, 2,6-dimethoxymethyl-p-cresol and 2,6-diacetoxymethyl-p-cresol; the thermally cross-linkable compounds each having three organic groups represented by Formula (6) such as TriML-P and TriML-35XL; those each having four organic groups represented by Formula (6) such as TM-BIP-A, TML-BP, TML-HQ, TML-pp-BPF, TML-BPA and TMOM-BP; and those each having six organic groups represented by Formula (6) such as HML-TPPHBA and HML-TPHAP.
Among them, typically preferred compounds are Bis-Z, TekP-4HBPA, TrisP-HAP and TrisP-PA; the compounds represented by Formula (5) such as BisPC-PCHP, BisTBC-PC, BI2MR-PC, BI4MC-PC, BIR-PAP, BIPC-PC, BIR-PC, BIR-PTBP, BIR-PCHP, 4PC, BIR-BIPC-F; the thermally cross-linkable compounds each having two organic groups represented by Formula (6) such as DML-MBPC and DML-MBOC, and the compounds represented by Formula (7) such as DML-OCHP, DML-PC, DML-PCHP, DML-PTBP, DML-POP, 2,6-dimethoxymethyl-4-t-butylphenol, 2,6-dimethoxymethyl-p-cresol and 2,6-diacetoxymethyl-p-cresol.
More preferred compounds are the compounds represented by Formula (5) such as BisPC-PCHP, BIR-PCHP and BIPC-PC; and the compounds represented by Formula (7) such as DML-OCHP, DML-PC, DML-PCHP, DML-PTBP, DML-POP, 2,6-dimethoxymethyl-4-t-butylphenol, 2,6-dimethoxymethyl-p-cresol and 2,6-diacetoxymethyl-p-cresol. 
By adding the compound (b) having a phenolic hydroxyl group, the resulting resin composition dissolves little in an alkaline developer before exposure, becomes readily soluble in the alkaline developer by action of exposure and thereby can easily be developed in a short time with less reduction in film thickness due to development.
The amount of the compound (b) having a phenolic hydroxyl group is preferably from 1 to 50 parts by weight, and more preferably from 3 to 40 parts by weight, relative to 100 parts by weight of the polymer component (a). Each of these compounds (b) having a phenolic hydroxyl group can be used alone or in combination.
Quinonediazide sulfonates (c) for use in the present invention are preferably compounds in which a naphthoquinonediazidosulfonic acid is bonded through an ester bond to a compound having a phenolic hydroxyl group. The compound having a phenolic hydroxyl group for use herein may be the same with, or different from, the compound (b) having a phenolic hydroxyl group. Preferred quinonediazide sulfonates (c) are compounds in which 4-naphthoquinonediazidosulfonic acid or 5-naphthoquinonediazidosulfonic acid is bonded through an ester bond to a compound such as Bis-Z, BisP-EZ, TekP-4HBPA, TrisP-HAP, TrisP-PA, BisOCHP-Z, BisP-MZ, BisP-PZ, BisP-IPZ, BisOCP-IPZ, BisP-CP, BisRS-2P, BisRS-3P, BisP-OCHP, Methylenetris-FR-CR and BisRS-26X (trade names, available from Honshu Chemical Industry Co., Ltd.), BIR-OC, BIP-PC, BIR-PC, BIR-PTBP, BIR-PCHP, BIP-BIOC-F, 4PC, BIR-BIPC-F and TEP-BIP-A (trade names, available from Asahi Organic Chemicals Industry Co., Ltd.), naphthol, tetrahydroxybenzophenone, methyl gallate, bisphenol A, methylenebisphenol or BisP-AP (trade name, available from Honshu Chemical Industry Co., Ltd.). Naturally, other quinonediazide sulfonates can be used in the present invention. Each of these quinonediazide sulfonates (c) can be used alone or in combination.
If the quinonediazide sulfonate (c) has a molecular weight of more than 1000, the quinonediazide sulfonate (c) cannot significantly be decomposed in a subsequent heat treatment, and thereby the resulting film of the resin composition may have deteriorated heat resistance, mechanical characteristics or adhesion. From this viewpoint, the molecular weight of the quinonediazide sulfonate (c) is preferably from 300 to 1000 and more preferably from 350 to 800. The amount of the quinonediazide sulfonate (c) is preferably from 1 to 50 parts by weight relative to 100 parts by weight of the polymer component (a).
The resin composition may further comprise various additives according to necessity within ranges not deteriorating the advantages of the invention. For example, in order to improve wettability between the photosensitive heat-resistant resin precursor composition and a substrate, the resin composition may comprise surfactants; ethyl lactate, propylene glycol monomethyl ether acetate, and other esters; ethanol and other alcohols; cyclohexanone, methyl isobutyl ketone, and other ketones; tetrahydrofuran, dioxane, and other ethers. In addition, silicon dioxide particles, titanium dioxide particles, and other inorganic particles or polyimide powders can be added to the resin composition.
To improve adhesion between the film of the resin composition and a substrate such as a silicon wafer, 0.5% to 10% by weight of a silane coupling agent, a titanium chelating agent or another additive can be added to the varnish of the resin composition. Alternatively, the substrate may be pre-treated with a solution of the additive.
In the former case, methyl methacryloxydimethoxysilane, 3-aminopropyltrimethoxysilane or another coupling agent, a titanium-chelating agent or an aluminum-chelating agent is added to the varnish in a proportion of from 0.5% to 10% by weight relative to the weight of the polymer component (a) in the varnish.
In the latter case, 0.5% to 20% by weight of the coupling agent is dissolved in a solvent, and the resulting solution is applied to the surface of the substrate by means of spin coating, dipping, spraying or steaming. In some cases, the substrate is heated at temperatures of 50xc2x0 C. to 300xc2x0 C. to accelerate the reaction between the substrate and the coupling agent. Such solvents for use herein include, for example, isopropyl alcohol, ethanol, methanol, water, tetrahydrofuran, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate, and diethyl adipate.
The resin composition of the present invention can yield a patterned heat-resistant resin, for example, in the following manner.
Initially, the resin composition is applied onto a substrate. Such substrates include, but are not limited to, silicon wafers, ceramics, gallium arsenide (GaAs), soda glass and quartz glass. The resin composition is applied to the substrate by spin coating using a spinner, spray coating, roll coating or another technique. The thickness of the applied film is generally set so that the thickness after drying falls within a range from 0.1 to 10 xcexcm, depending on the coating technique, the solid concentration and viscosity of the resin composition and other factors.
Next, the substrate carrying the resin composition is dried to yield a film of the resin composition. The drying operation is preferably performed using an oven, hot plate or infrared rays at temperatures of from 50xc2x0 C. to 180xc2x0 C. for 1 minute to several hours.
The film of the resin composition is then irradiated with and exposed to actinic radiation through a desirably patterned mask. Such actinic radiation for exposure includes ultraviolet rays, visible light, electron beams, and X rays. Among them, i-line (365 nm), h-line (405 nm) or g-line (436 nm) from a mercury lamp is preferably used in the present invention.
To pattern the heat-resistant resin, exposed portions of the resin film are removed by using a developer. As the developer, an aqueous solution of a compound exhibiting alkalinity is preferred. Such compounds exhibiting alkalinity include, for example, tetramethyl ammonium, diethanolamine, diethylaminoethanol, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylamine, methylamine, dimethylamine, dimethylaminoethyl acetate, dimethylaminoethanol, dimethylaminoethyl methacrylate, cyclohexylamine, ethylenediamine and hexamethylenediamine. According to necessity, additional components can be added to the aqueous solution. Such additional components include, for example, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, gamma-butyrolactone, dimethylacrylamide, and other polar solvents; methanol, ethanol, isopropyl alcohol, and other alcohols; ethyl lactate, propylene glycol monomethyl ether acetate, and other esters; cyclopentanone, cyclohexanone, isobutyl ketone, methyl isobutyl ketone, and other ketones. Each of these additional components can be used alone or in combination. After developing, the film is rinsed with water. The water for rinsing may further comprise ethanol, isopropyl alcohol, and other alcohols; ethyl lactate, propylene glycol monomethyl ether acetate, and other esters.
After developing, the film is heated at temperatures of from 180xc2x0 C. to 500xc2x0 C. and is thereby converted into a heat-resistant resin film. In this procedure, the film is heated for 5 minutes to 5 hours by selecting a temperature and elevating the temperature in stages or by selecting a temperature range and continuously elevating the temperature. For example, the film is heated at 130xc2x0 C., 200xc2x0 C. and then 350xc2x0 C. for each 30 minutes, respectively, or the temperature is linearly elevated from room temperature to 250xc2x0 C. over 2 hours or from room temperature to 400xc2x0 C. over 2 hours.
The heat-resistant resin film prepared by using the resin composition of the present invention can be used as a passivation film of a semiconductor, a protective film of a semiconductor device, an insulating layer in a display device carrying an organic electroluminescent device.
The insulating layer formed by using the resin composition of the present invention is used in a display device comprising a substrate, a first electrode formed on the substrate, and a second electrode facing the first electrode. Specifically, such display devices include, for example, liquid crystal displays (LCDs), electrochromic displays (ECDs), electroluminescent displays (ELDs) and display devices using organic electroluminescent devices (organic electroluminescent units). The organic electroluminescent unit is a display device comprising an organic electroluminescent device including a substrate, a first electrode formed on the substrate, a thin film layer containing at least a luminescent layer composed of an organic compound, and a second electrode formed on the thin film layer.
The present invention will be illustrated in further detail with reference to several examples and comparative examples below, which are not intended to limit the scope of the invention. The characteristics of resin compositions obtained in the examples and comparative examples were evaluated by the following methods.
Preparation of Photosensitive Polyimide Precursor Film
A sample photosensitive heat-resistant resin composition (hereinafter referred to as xe2x80x9cvarnishxe2x80x9d) was applied onto a 6-inch silicon wafer, so that the film after prebaking had a thickness of 1.5 xcexcm, and was prebaked at 120xc2x0 C. for 3 minutes using a hot plate (available from DAINIPPON SCREEN MFG. CO., LTD. under the trade name of xe2x80x9cSCW-636xe2x80x9d) and thereby yielded a film of a photosensitive polyimide precursor.
Measuring Method of Film Thickness
The thickness of the sample film was determined at a refractive index of 1.64 using a film thickness measurement system (available from DAINIPPON SCREEN MFG. CO., LTD., under the trade name of xe2x80x9cLambda Ace STM-602xe2x80x9d).
Exposure
A Nikon test pattern (available from Nikon Corporation, Japan) was set to an exposure system (available from Canon Inc., Japan under the trade name of xe2x80x9cContact Aligner PLA 501Fxe2x80x9d), and the sample film was exposed to total ultraviolet rays at an irradiance of 10 mW/cm2 (in terms of 365 nm) for a predetermined time.
Development
The sample film was developed by immersing the same in a developer, a 2.38% aqueous solution of tetramethylammonium hydroxide, at 23xc2x0 C. for 60 seconds, was then rinsed with water for 20 seconds and was dried.
Calculation of Film Residual Rate
The film residual rate was calculated according to the, following equation:
Film residual rate (%)=[(Film thickness after development)/(Film thickness after prebaking)]xc3x97100 
Calculation of Sensitivity
The sensitivity of the sample film after exposure and development was defined as the exposure (hereinafter briefly referred to as xe2x80x9coptimum exposurexe2x80x9d) to reproduce a 50-xcexcm line-and-space pattern (1L/1S) with a line-and-space width of 1:1.
Calculation of Resolution
The resolution of the sample film after exposure and development was defined as the minimum pattern size to reproduce a 50-xcexcm line-and-space pattern (1L/1S) with a line-and-space width of 1:1 at the optimum exposure.